1. Field of the Invention
The present invention relates to lifting devices, in general, and to a lifting shoe system for sheet lifting equipment, in particular.
2. Description of the Prior Art
A lifting device, commonly referred to as a sheet lifter, sheet package lifter or sheet grab, is widely used in the steel, other metals, glass and transportation industries. Such a device is usually suspended from an overhead crane or hoist and is used to hook, raise and transport material which is usually positioned horizontally, and either single or multi-stocked, such as sheets of metal, glass, paper, etc. Such material further can be either palletized or non-palletized.
In operation, the lifter is positioned above the sheet or sheet package (commonly referred as the "lift") and then lowered so that the lifting shoes of the lifter can be run under the edge of the lift. Sheet lifters have been proven to be the best and safest devices to handle and transport sheet packages. However, because the lifting shoes of sheet lifters are of a fixed design (i.e. no lateral adjustment), a typical lifter cannot be used universally on all types of sheet packages.
The present lifting shoe component of a sheet lifter is usually fabricated from a continuous, elongated, one-piece angle member. Such solid, continuous lifting shoes are used on most sheet lifters; however, they prohibit the use of the lifter on packages having full-width cross runners extending therebeneath, and on packages having longitudinal runners therebeneath and bounded by circumferential bands. The full-width cross runners prohibit such a shoe from being inserted under the package. And, in the case of packages having longitudinal runners and circumferential bands, it is possible to insert the solid continuous lifting shoe under skids previously placed beneath the circumferential bands. However, when the package is lifted, the shoe of the sheet lifter snaps all of the circumferential bands.
In an effort to increase the utilization and flexibility of sheet lifters, a few manufactures have cut notches in their lifting shoes to allow the shoes to straddle the full width cross runners and under-runner circumferential bands. However, because of various length packages, it is often the case that the full-width cross runners and under-runner circumferential bands cannot be so located so as to enable the notches in the lifting shoe to straddle these obstructions.
It is therefore an object of the present invention to provide a lifting shoe system for sheet lifting devices which is universally adaptable to lift all types of sheet packages, including packages having full-width cross runners or under-runner circumferential bands.
It is a further object of the invention to provide an adjustable lifting shoe system for sheet lifting devices.
It is a further object of the invention to provide a system for sheet lifting devices wherein the lifting shoe system is formed of a plurality of adjustable shoe members or forks.
Still other objects and advantages will become apparent when one considers the attached drawings and the description of the invention presented hereinbelow.